1144-P: Maternal Exercise Alters the Human Milk Metabolome—Associations with Infant Thermogenesis

Breastfeeding reduces childhood obesity risk, though the mechanisms remain unclear. We recently reported that maternal exercise significantly increases breastmilk levels of lipids and metabolites involved in brown adipocyte thermogenesis. It is unclear whether differences in these milk constituents may play a functional role in infant adipose tissue metabolism. Thus, we tested whether consumption of human milk after an acute bout of maternal exercise alters infant thermogenesis, a surrogate for brown adipose tissue function.

Exclusively breastfeeding mothers (n=31, 1-mo postpartum) completed a supervised exercise session (45 minutes, heart-rate reserve 65-75%) and, on a separate day, a control period of rest, each followed by an infant feeding session 1h afterwards. We analyzed human milk (metabolomics, lipidomics) before and after exercise. We compared infant anterior neck surface temperature (infrared thermography, IRT) following feeding of either “exercise milk” or “control milk”. We analyzed resting metabolic rate (RMR) and body composition (DXA) in all infants; a subset (n=10) also underwent fat-fraction MRI to assess sub-clavicular beige fat depot volume.

Infant temperature trended higher (+0.245°C, P=0.1) after consumption of “exercise milk” vs. “control milk”; higher delta temperature was associated with higher infant trunk fat free mass (P<0.05). Of 213 metabolites detected in breastmilk; 37 were nominally changed (P<0.05) and 3 significantly changed (FDR<0.05) by exercise. For 16 metabolites, the change in abundance with maternal exercise correlated with change in infant temperature after "exercise-" vs. "control-milk" consumption. Top-ranking positively correlated metabolites included signaling lipids, lactate, guanine, and spermine (P<0.05).

Our findings indicate that exercise-induced changes in human milk are associated with activation of infant metabolism via thermogenesis.